What does x[:]=[4,5,6] mean?

[Indirect Meowbot]

"Franz GEIGER" <fgeiger at datec.at> wrote:

> In site.py I saw
> sys.path[:] = L
> What does this mean? Why is the '[:]'? Why not simply
> sy.path = L ?

In a language like C you have to work a little bit harder to get a
pointer to something.  In Python, you have to work a little bit harder
_not_ to get just a reference.

>>> meow = [1,2,3]
>>> woof = meow
>>> meow[0] = 42
>>> print meow, woof
[42, 2, 3] [42, 2, 3]
>>> # Ewww!
... 
>>> meow = [1,2,3]
>>> woof[:] = meow
>>> meow[0] = 42
>>> print meow, woof
[42, 2, 3] [1, 2, 3]
>>> # Yay.